Simply designed, easy-to-use and highly compatible electronic devices will be the main stream in the future. To increase the compatibility, digital carriers are connected to optical lenses so that the digital carriers image objects and instantly show the images of the objects. 3-C products such as cell phones, Webcams and laptop computers are equipped with optical lenses. As the electronic devices are getting lighter and smaller, the optical lenses must also be getting lighter and smaller so that the optical lenses can be used in the digital carriers. The pixel number and the image quality are also important factors taken into consideration by a customer. A cell phone equipped with a camera providing two million pixels is not satisfactory.
There is a conventional four-piece imaging lens module including four lenses. The fourth lens includes at least one convex surface near the optical axis on the side of an object. A digital carrier equipped with the four-piece imaging lens module provides more than two million pixels, but fails to provide good image quality, high color saturation and small optical length because of the convex surface of the fourth lens.
Moreover, the fourth lens includes a convex surface on the side of an object so that the optical length cannot be reduced effectively and that the fabrication is difficult. Therefore, it is not competitive in the market. The yield of the four-piece imaging lens module is lower than expected.
The present invention is therefore intended to obviate or at least alleviate the problems encountered in prior art.